1. Technical Field
The invention relates to a device for carrying out a leak test on a fuel rod capsule containing at least one fuel rod and test gas, the device comprising a test container which is designed for accommodating at least one fuel rod capsule and which is lowerable into a water-flooded pool of a nuclear plant. The invention further relates to a method for carrying out the leak test on the fuel rod capsule containing at least one fuel rod and test gas, using such a device.
2. Background and Relevant Art
It is known that fuel rods of nuclear reactors may develop leaks during operation; i.e., water may penetrate into the fuel rods. As soon as a fuel rod with such a defect is identified, it is typically encapsulated underwater in a fuel rod capsule in order to counteract escape of radioactive fission products, in particular radioactive gases. The encapsulation of the fuel rod takes place at a sufficient depth that the opening and closing of the fuel rod capsule takes place by remote control by means of suitable manipulators. After the fuel rod capsule is opened and the fuel rod is inserted, the water that has penetrated into the fuel rod capsule is displaced by blowing in a test gas, and the fuel rod capsule is transferred into an encapsulation device. In this encapsulation device, the fuel rod situated in the fuel rod capsule is heated by passing hot test gas through the fuel rod capsule, thus evaporating the water present in the fuel rod. After the water vapor has been removed from the encapsulation device by drying the test gas or replacing the moist gas with dry test gas, the fuel rod capsule is closed and welded at the closure point. After the welded, and thus leak-tight, fuel rod capsule is removed from the encapsulation device, the fuel rod capsule must be further tested for leak-tightness. The fuel rod capsule containing the fuel rod is then optionally temporarily stored in a spent fuel pool filled with water before it can be transported to a final repository or a reprocessing plant.
It is known to test the fuel rods per se or the fuel rod capsule containing the at least one fuel rod for leak-tightness.
A method for testing the leak-tightness of fuel rods is known from DE 195 42 330 A1, for example, in which gases that escape from the fuel element are analyzed for their gaseous fission product content.
WO 2007/071337 describes the testing of fuel rod capsules containing at least one fuel rod. The fuel rod capsule is introduced into a test container situated inside a flooded pool of a nuclear plant, beneath the water surface. Leaks are detected by means of an underwater camera, and a leak rate is estimated based on the number and size of the detected gas bubbles.